| 07 Jul 2025
Local and remote climatic drivers of extreme summer temperatures in the Arabian Gulf
Abstract. The Arabian Gulf (also known as the Persian Gulf; hereafter simply the Gulf) is a shallow, subtropical, semi-enclosed sea that experiences the highest average summer sea surface temperatures (SSTs) in the global ocean. While local marine organisms have adapted to these extreme conditions, interannual temperature fluctuations result in occasional marine heatwaves that trigger mass coral bleaching and other ecological impacts. However, the climatic drivers of this variability remain poorly understood. In this study, we investigate the sources and mechanisms behind extreme summer temperatures in the Gulf. Analyzing a regional eddy-resolving ocean hindcast simulation combined with ERA5 reanalysis data, we find that extreme summer surface temperatures are tightly linked to lower-than-normal surface pressure over the Arabian Peninsula and higher-than-normal surface pressure over Iran and Pakistan. These pressure anomalies are typically associated with stronger monsoonal winds in the western Arabian Sea and weakened local winds. Enhanced monsoon circulation leads to (i) increased evaporation over the Arabian Sea and greater moisture transport into the Gulf in the lower troposphere, trapping heat near the surface, and (ii) enhanced subsidence over the Arabian Peninsula and the Gulf in the upper troposphere, inducing further surface heat retention. Meanwhile, weakened local Shamal winds – particularly in the northern Gulf – reduce evaporative cooling and facilitate the accumulation of moist, warm air, amplifying local warming. These regional atmospheric changes are strongly modulated by large-scale climate variability modes, with El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) together explaining over 50 % of the observed interannual SST variability in the Gulf. La Niña (El Niño) and the negative (positive) phase of the NAO both favor weaker (stronger) Shamal winds and warmer (cooler) SSTs during the peak summer months over the Gulf. Additionally, La Niña (El Niño) is associated with stronger (weaker) monsoon winds in the southern and western Arabian Sea, leading to stronger and more persistent warming (cooling) anomalies in the Gulf. The influence of these teleconnections is additive, with the warmest summers occurring when La Niña and negative NAO phases coincide. These findings have implications for the predictability of summer marine heatwaves and associated ecosystem risks in the Gulf.
Comments:
This study examines sea surface temperature (SST) variability in the Persian Gulf and its relationship with large-scale climate patterns (ENSO, NAO and IOD).
climate patterns (ENSO, NAO and IOD). The authors indicated that local atmospheric anomalies significantly impact SSTs in the Gulf by modulating heat fluxes. ENSO, NAO and IOD could impact SSTs in the Gulf by modulating the local atmosphere.
circulation. The combined effect of ENSO and NAO on SSTs in the Gulf is also discussed. The results obtained in this study are interesting. This manuscript can be accepted after revisions.
To confirm the results obtained from the ERA5, the authors should use other reanalysis data (e.g. MERRA2 and JRA55).
It should be noted that ENSO, IOD and NAO are not independent of each other. For instance, ENSO can affect IOD, IOD can affect ENSO, and NAO can also affect ENSO. The authors should examine the combined and relative effects of ENSO, IOD and NAO on SSTs in the Gulf using partial composite or regression analysis.
In addition to ENSO and the NAO, I would suggest that the authors also examine the role of Arctic sea ice anomalies in shaping extreme temperatures in the Gulf. Recent studies have indicated that Arctic sea ice anomalies could have a significant impact on ENSO, NAO and IOD. I suggest add some discussions. (https://doi.org/10.1175/JCLI-D-24-0419.1.; https://doi.org/10.1038/s41612-025-00936-x.; https://doi.org/10.1175/JCLI-D-23-0733.1.).
In addition to atmospheric heat fluxes, the tendency of SST should also be significantly impacted by oceanic dynamics, such as advection and upwelling/downwelling. The authors should analyse the SST tendency equation and investigate the role of these oceanic processes.
The authors discussed the possible influence of ENSO, NAO and IOD on SST anomalies in the Gulf. However, the underlying physical mechanisms have not been investigated in detail. The authors should examine the physical processes through which ENSO and NAO impact the formation of local atmospheric circulation. For example, Cheng et al. (2023; https://doi.org/10.1007/s00382-022-06616-3) indicated that AO/NAO-related atmospheric heating over the North Atlantic could trigger an atmospheric wave train from the North Atlantic to the northern Indian Ocean.